■P地址是分配给主机的网络接口 ▣一个主机可能有多个网络接口 Internet socket ■IP Address,Port ■P地址与接口相关 Solving mobility below IP layer is attractive IP Point of Attachment remain static Mobility is hidden from Correspondent Node Data Link layer domain cover area ▣Big or small area ◼ IP地址是分配给主机的网络接口  一个主机可能有多个网络接口  Internet socket ◼ IP Address，Port ◼ IP地址与接口相关 ◼ Solving mobility below IP layer is attractive  IP Point of Attachment remain static  Mobility is hidden from Correspondent Node ◼ Data Link layer domain cover area  Big or small area